Heretofore, in the production of Koji, steam cooked materials such as rice, wheat, cereals and the like are inoculated with koji-mold and charged in a Koji-tray and cultured at about 30.degree. C, wherein inoculation is generally carried out while the raw material is warm. The temperature thereof is reduced to 26.degree. C during a period of 2 hours after the mori-operation thus preventing entry of infectious microbes therein owing to the lower temperature and promoting the germination. With a lapse of time of about 18 hours therefrom, the temperature of the material rises to about 30.degree. C owing to the respiration heat, and therefore a first treatment-by-hand is carried out to put fresh air therein. Owing to the treatment-by-hand, the temperature of the material lowers to about 27.degree. C, however after a period of approximately 25 hours the temperature again rises to approximately 30.degree. C as a result of heat generation. At this point, a second treatment-by-hand is carried out to attain sufficient cooling and sufficient supply of air and thus after approximately 50 hours the product of Koji is discharged. Such a prior art method has been thought ideal. As is apparent from the above operation, it is an absolutely necessary condition in the production of Koji to suppress propagation of infectious microbes and to control temperature, humidity and supply of oxygen.
In order to meet such a condition, Koji making systems in which the entire system is arranged in a closed type system have been known, however in these known systems, adjustment of temperature and humidity of the Koji making chamber is carried out by causing the used gas to pass a warm water shower and thereafter again be supplied to the Koji making chamber. However, this method has the following significant drawbacks. Namely, first, the circulation gas in the system is subjected to heat exchanging with warm water for resue thereof, and as a result of the use of such warm water the droplets contained in the gas become very large, so that when using a supersaturation humidity the droplets are undesirably applied to the Koji. Secondly, the used warm water is thrown away as waste water or recirculated to use; however, in the former case its treatment is not easy and in the latter case the sterilization is not sufficient, so that the warm water provides a propagation field for infectious microbes. Thirdly, the gas after passing through the warm water shower contains an excess amount of moisture since droplets are large, very wet gas is produced, which is a decisive drawback.
Moreover, in these known systems, temperature adjusting systems of the Koji making chamber are all arranged in such a manner that gas feeding in to the chamber is directly fed into the Koji making chamber as it is from the beginning subjected to controlling of temperature and humidity, wind volume, and wind flow rate. Accordingly, the following drawbacks are inevitable. Namely, in the course of arriving at an inlet of the Koji making chamber from a gas generating source, there are losses of temperature, wind flow rate and wind volume owing to passage through cyclones for dust removal, addition of temperature and humidity, and in addition to such energy losses, further difficulties are such that, in order to control temperature, fans and cyclones should be finely regulated each time, and these regulations are usually inaccurate, and very difficult operations. Moreover, in order to meet the necessary conditions for the Koji making chamber, timelag is inevitably produced.
According to the prior art methods, in any case, ducts and fans etc. are inevitably applied with fine powder of raw material, dusts and water droplets, and these methods are always accompanied by danger of contamination from infectious microbes, particularly aerobic microbes. Once the system is contaminated by infectious microbe, not only the relevant batch products must be thrown away, but also the sytem must be subjected to sterilization treatment, with the result of inevitablely large damage.